Wireless communication networks and the Internet network are expanding rapidly and their number of users is increasing. Introducing advanced Internet services into digital mobile stations of wireless communication networks, such as so-called media phones, is possible, e.g. with the aid of WAP technology. WAP is an open standard designed to globally support the majority of digital wireless communication networks, such as GSM (Global System for Mobile Communications), GPRS (General Packet Radio Service), PDC (Personal Digital Cellular), CDMA IS-95 (Code Division Multiple Access), TDMA IS-136 (Time Division Multiple Access) and third generation networks, such as WCDMA (Wideband CDMA) and CDMA-2000. Because the WAP system was developed only recently and because the WAP system specifications in some cases only define the frameworks for different implementations, there exist no known solutions for the implementation of certain functions of the WAP system.
In the WAP system (FIG. 1), a wireless terminal or mobile station MS, here a so-called WAP terminal, that uses WAP protocols for external communication can communicate with a server 20 of the Internet network. The connection between the WAP terminal and the Internet network is implemented by a WAP gateway 15, which operates as a message transmission element between the WAP terminal MS and an Internet network 18. The WAP gateway 15 converts messages directed by the WAP terminal to the Internet network 18, as necessary, into messages according to some Internet protocol, such as the TCP/IP protocol (Transmission Control Protocol/Internet Protocol). Correspondingly, messages addressed from the Internet network 18 to a WAP terminal MS of a wireless network 12, are converted as necessary in the WAP gateway 15 into messages according to WAP protocols (e.g. WSP, Wireless Session Protocol). The WAP terminal MS can be any device that uses WAP protocols for external communication, such as a mobile station of a cellular network or a computer terminal, which is in communication with the wireless network 12, e.g. via a mobile station of a cellular network.
Communication modes supported by WAP, intended for information transfer over a radio path are called bearers. In different networks supporting WAP these are, among others, SMS messages (Short Message Service), data calls (CSD, Circuit Switched Data) and packet radio, i.e. GPRS services, USSD service (Unstructured Supplementary Service Data), as well as other bearers defined in the WAP specifications.
As far as its protocols are concerned, the WAP system is a hierarchical system. Both a WAP terminal and a WAP gateway comprise a WAP protocol stack implemented as software comprising specific WAP protocol layers. The WAP protocol layers are, among others, a WSP layer (Wireless Session Protocol), a WTP layer (Wireless Transaction Protocol) and a WDP layer (Wireless Datagram Protocol). The corresponding protocol layers of a WAP terminal and a WAP gateway communicate with each other to implement reliable data transfer between the WAP terminal and the WAP gateway, over a specific bearer.
For a long time users of computer terminals connected to the Internet network have had the opportunity to retrieve multimedia components, such as images, text, short video clips and audio clips in electronic format, into their computer terminals from some server of the Internet network. As data transfer rates increase and the properties of mobile stations improve, interest in a multimedia messaging service for wireless networks has now also been awakened. However, in connection with the WAP system, for example, no solution has so far been presented for implementing such a multimedia messaging service.
International patent application WO 98/19438 presents a solution for implementing a multimedia messaging service in a telecommunication network. The multimedia messaging system presented in document WO 98/19438 comprises a multimedia message store, in which a multimedia message addressed to a specific user is stored. The user is provided with an opportunity to communicate the multimedia presentation properties of his terminal equipment to the multimedia messaging system, which translates said multimedia message either partly or fully, taking into consideration the multimedia presentation properties of the user's terminal. After this, the multimedia messaging system sends the multimedia message to the user' terminal. In the multimedia messaging service presented by document WO 98/19438, the multimedia messaging system is substantially in control of multimedia message delivery, and the document focuses almost totally on the translation of multimedia messages.
When implementing a multimedia messaging service in connection with wireless communication systems, new problems arise due to the limited capacity of wireless terminals and the radio paths used for communication.
A multimedia messaging service for third generation mobile communication networks, such as WCDMA, has been proposed which would be implemented in a manner similar to a short message service, i.e. substantially by pushing messages addressed to a wireless terminal, stored in a specific messaging centre, to the wireless terminal as soon as it can be contacted. However, pushing multimedia messages to a wireless terminal causes problems. Due to the limited memory capacity of a wireless terminal, such as a mobile station of a cellular network, a multimedia message will not necessarily fit into the terminal's available memory. A multimedia message pushed to a wireless terminal may also comprise elements which the wireless terminal is unable to process, whereupon these said elements are sent to the wireless terminal needlessly, wasting radio resources.